Many eye diseases such as glaucoma and dry eye are topically treated with eyedrop solutions. The frequency and duration of eyedrop therapy is dependent on the type of disease being treated and the individual patient's specific needs. For example, some diseases require continuous eyedrop application for the life of the patient, whereas others require frequent eyedrop application for relatively short periods of time. Such topical treatment of an eye disease is only effective if the eyedrops are properly administered to the eyes at the frequency and for the duration required by a particular patient and disease.
Since it can be inconvenient to manually apply eyedrop solutions with the necessary frequency and duration, and since some patients exhibit a reluctance or disregard for the consistent application of such medications, a number of eyedrop delivery systems have been developed which automatically apply the necessary medication to the eyes without patient intervention. Presently, there are four basic types of eyedrop delivery systems which have been developed. Such systems include insert devices, externally worn devices, semi-implants and full implants. Unfortunately, however, each of the present systems has proven unsatisfactory for proper and effective administration of eyedrop therapy.
Insertable systems generally consist of impregnating a contact lens-like matrix with medication and then placing the drug-impregnated contact lens-like matrix on the surface of the eye. The medication is then distributed over the eye by the blinking motion of the eyelid. This insert technique initially requires the presence of some natural tears (or an artificial moistener) for insertion of the device, as well as subsequent continuous voluntary blinking to distribute the medication. This method has also been known to cause discomfort and can be costly. Moreover, the insert technique cannot be utilized when a relatively large volume of fluid is required for proper treatment.
Externally worn devices generally comprise a system whereby fluid is transported from a fluid reservoir to the eyes via tubing which is mounted on some type of support structure, e.g. eyeglass frames, which is worn by the patient. Several different arrangements of externally worn devices have been proposed.
One arrangement features a fluid reservoir mounted directly on the support structure. Fluid flow to the eyes is activated by precise positioning and nodding of the head. With this system, fluid flow to the eyes is relatively unmanageable and unreliable.
Another arrangement has one end of the tubing positioned on the lower eyelid, or in the cul-de-sac of the conjunctivia, and the other end of the tubing connected to the fluid reservoir which is contained within a syringe whose plunger is activated by compressed gas generated by an electrolytic process. This arrangement can irritate and even injure the eye. Another disadvantage of this device is the toxicity of the electrolyte which is used to generate the gas which activates the plunger. Both the toxic electrolyte and the fluid reservoir are contained in the same syringe, thereby creating a risk of contamination of the fluid supply. This system also requires tedious maintenance which cannot be performed by the average patient.
A further arrangement of externally worn devices features a contact lens-like device adapted to be connected to the end of the tubing. Blinking motion of the eyelid compresses the contact lens/tube assembly to distribute solution over the surface of the eye. Such devices are uncomfortable to wear, require continuous voluntary blinking and are susceptible to contamination.
The semi-implant device is similar to a number of the foregoing in the sense that tubing is used to transport fluid from a reservoir to the eyes; however, part of the tubing is surgically implanted under the skin around the eyes and the tip of the tubing is surgically secured in the conjunctival area. This technique eliminates the need for eyeglasses or other support structure adjacent the eyes, but exposes the patient to the risks associated with surgical intervention.
The full implant device consists of implanting the whole system (i.e., pump, reservoir, and tubing) under the skin. This technique also exposes the patient to the risks associated with surgical intervention.